1. Technical Field
The present invention relates to a projection display apparatus and a display method, and more particularly, to a technique of correcting a keystone distortion of an image displayed on a projection plane in a projection display apparatus and a display method.
2. Related Art
When an image is displayed on a screen using a projector, a keystone distortion may occur in the image (hereinafter, referred to as “display image”) displayed on the screen depending on the angle of the screen relative to the projector. In this case, a technique of making a keystone correction for correcting the keystone distortion of the display image is known.
The keystone correction is made by capturing a screen with an image capturing unit such as a CCD camera, detecting the images of frame sides of the screen from the captured image, and reducing and forming an image in a keystone form on a liquid crystal panel of the projector on the basis of the detected image of the frame sides of the screen. (for example, see JP-A-2006-60447).
However, in the above-mentioned technique, there is a problem that an image (for example, an image of a fluorescent lamp or the like reflected in a screen), which is not actually the image of any of the frame sides of the screen, may be erroneously detected as the image of the frame side from a captured image and thus the keystone correction is not properly performed.
This problem is common to keystone corrections of images in general projection display apparatuses displaying an image on a projection plane by projection, as well as the keystone correction at the time of displaying an image on the screen by the use of a projector.